The hydrolysis of proteins to produce food ingredients is well known. For example, U.S. Pat. No. 4,165,391 (Corbett) discusses the use of hydrolysed vegetable proteins (HVP) as flavoring agents for providing meaty flavor and/or flavor intensity to foods. Corbett notes that acid hydrolysis of vegetable proteins is the most important method (as compared with enzymic hydrolysis and alkaline hydrolysis) from the standpoint of food products and that hydrochloric or sulfuric acid is generally used in the hydrolysis.
The use of hydrochloric acid in the hydrolysis of proteins has bee implicated in the production of chlorohydrins from residual glycerol in the protein source. J. Velisek et al., "Chlorohydrins in Protein Hydrolysates", Z. Lebensm. Unters. Forsch, vol. 167, pp. 24-44 (1978). Methods of removing chlorohydrins or preventing their formation are discussed in U.S. Pat. No. 4,759,944 (Fasi et al.). Fasi et al. state that preventing the formation of chlorohydrins is impractical without altering the organoleptic qualities (e.g., taste) of the hydrolysed protein. Likewise, decolorizing with carbon or rectification (i.e., fractional distillation) to remove chlorohydrins are characterized as impractical. Fasi et al. disclose a method for removing chlorohydrins from hydrolysed protein which involves subjecting the hydrolysed protein to steam distillation under reduced pressure while keeping the density of the hydrolysed protein substantially constant.
European Patent Application No. 89202368.0, filed Sept. 20, 1989, and published Apr. 4, 1990, as E.P.O. Publication No. 0361596, disclosed a method of hydrolysing protein with hydrochloric acid. It is stated that the reaction is initially carried out at between 60.degree. C. and 97.degree. C. and that the reaction temperature is further increased to 100.degree. C. to 110.degree. C. and held prior to cooling and neutralizing. It is also stated that a further reduction in the amount of chloropropanols in the hydrolysate may be obtained by steam distillation or gel filtration or by hydrolysis of chloropropanols.
European Patent Application No. 89202369.8, filed Sept. 20, 1989, and published Apr. 4, 1990, as E.P.O. Publication No. 0361597, discloses subjecting an aqueous solution of hydrochloric acid-hydrolysed protein to gel permeation chromatography using a porous material having an equivalent pore diameter between 0.5 and 2.0 nanometers and eluting a fraction which is free of detectable amounts of chloropropanols.
European Patent Application No. 89202367.2, filed Sept. 20, 1989, and published Apr. 4, 1990, as E.P.O. Publication No. 0361595, discloses a process for improving a hydrochloric acid-hydrolysed protein by subjecting an aqueous solution thereof to the conditions which cause hydrolysis of chloropropanols therein, e.g., a pH between 5.5 and 8.0 and a temperature between 20.degree. C. and 180.degree. C. for a period of between 10 days to 15 minutes.
European Patent Application No. 89118189.3, filed Sept. 30, 1989, and published Apr. 18, 1990, as E.P.O. Publication No. 0363771, discloses a process for the production of a hydrolysed protein using hydrochloric acid wherein the hydrolysate is treated with alkali and held at a pH of from 8 to 14 to reduce the amount of undesirable chlorinated compounds.